Rural fire crews are responding to dozens of fires across Australia’s southeast, as officials warn residents to prepare for what could be the worst fire danger day in New South Wales' history.

A total fire ban will be in place across NSW on Tuesday with temperatures in the state’s far west predicted to hit 45C, while the mercury is forecast to climb to 43C in Sydney - the third highest on record.

NSW Premier Barry O'Farrell on Monday made an emphatic appeal to all state residents to be fully prepared for the worst.

"Tomorrow is not just going to be in the 40s, it will perhaps be the worst fire danger the state has ever faced," he said.

"Don't just think, 'Tomorrow is another bush fire danger day, tomorrow is another summer's day'. Tomorrow is going to be the worst fire danger day in parts of this state we've ever experienced in history."

A total fire ban has been applied for NSW from midnight on Monday.

EXTREME HEAT: Christchurch firefighter John Barnes will help fight bushfires in Australia.

The Fire Service has advised residents never to attempt to stay and defend their homes when threatened by fire on a day rated catastrophic.

National parks will be closed and nursing homes evacuated as the state sets to sizzle.

O'Farrell urged campers and holidaymakers to leave early Tuesday morning as thousands of fire service personnel would be on heightened standby.

"Rethink your need to be in the bush, have a bush fire plan, be prepared but most importantly make sure you are well away from harm's way," he said.

FARMING TOWN UNDER THREAT

A massive bushfire could potentially double in size and hit small farming communities in Victoria’s southwest, as the north of the state faces severe conditions.

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There is a threat to lives and property with the southwest Victorian settlement of Drik Drik under direct attack from fire and embers, authorities said on Monday night.

An afternoon wind change swung the 4000-hectare Kentbruck fire on a path to Drik Drik, an agricultural farming area of about 30 houses.

Authorities warned the out-of-control bushfire had the potential to double in size to 8000 hectares in an afternoon with westerly to south-westerly winds of up to 40kmh on Tuesday capable of pushing the fire a significant distance.

Fire Services commissioner Craig Lapsley said the immediate concern on Monday night was the Drik Drik area but the key issue would be on Tuesday.

‘‘It will be a fire that will be pushed with winds and we believe that it’s got the potential to move significant distance tomorrow, potentially block the Princes Highway and have further impacts on the rural community around Drik Drik and Dartmoor,’’ Lapsley told ABC TV.

Nearly 500 firefighters and a dozen aircraft are battling the blaze, which started on Friday and has mainly burnt through pine plantation.

FIREFIGHTER INJURED AS BLAZE OVERTAKES TRUCK

A firefighter has been injured battling a blaze near southern NSW town of Gunning this afternoon when the fire overtook his truck.

The fire broke out between Gunning and the Bellmount Forest and has raced through more than 25 hectares of scrub.

The Snowy Hydro Southcare helicopter has been deployed to transport the man to Canberra Hospital. A NSW Rural Fire Service spokeswoman said the injured firefighter was in a stable condition but could not provide any further details

PRAISE FOR FIREFIGHTERS IN TASMANIA

Australian Prime Minister Julia Gillard said firefighters battling bushfires sparked by a heat wave in Tasmanian are ''showing great Australian mateship''.

Gillard has been touring the island state, where fires burning since last week have destroyed dozens of homes and forced hundreds of people to evacuate.

Gillard said all of Australia was standing with Tasmanians at this difficult time.

''To all of those people, we are thinking of you in moments of grief and despair,'' she said.

''A number of people know their home has been destroyed but as yet for safety reasons they haven't been able to see the damage for themselves.''

Gillard said she had met Victorian firefighters who were returning the favour to their Tasmanian counterparts, who helped them out in the 2009 blazes.

The fires on the island state were so far fatality-free police said after a search of one of the worst-hit towns.

Police searched 335 properties in and near Dunalley, a village on the state's east coast, but have not found any bodies.

In a statement, Tasmanian police said they would search south of the town in Murdunna and Sommers Bay today.

But many people are still unaccounted for, the statement said.

The grim task comes as fire authorities warn bushfires that have ravaged the south-east of the state could flare up again as more warm weather hits.